>>> On 11/22/2012 at 05:29 PM, in message <50adaa26.7080...@ilyx.ru>, Ilya Zykov <i...@ilyx.ru> wrote: > On 22.11.2012 4:47, andrew mcgregor wrote: > > > > > >>>> On 11/22/2012 at 10:39 AM, in message <50ad4a01.7060...@ilyx.ru>, Ilya > >>>> Zykov > > <i...@ilyx.ru> wrote: > >> On 22.11.2012 1:30, Alan Cox wrote: > >>>> Function reset_buffer_flags() also invoked during the > >>>> ioctl(...,TCFLSH,..). At the time of request we can have full buffers > >>>> and throttled driver too. If we don't unthrottle driver, we can get > >>>> forever throttled driver, because after request, we will have > >>>> empty buffers and throttled driver and there is no place to unthrottle > >> driver. > >>>> It simple reproduce with "pty" pair then one side sleep on > >>>> tty->write_wait, > >>>> and other side do ioctl(...,TCFLSH,..). Then there is no place to do > >> writers wake up. > >>> > >>> > >>> So instead of revertng it why not just fix it ? Just add an argument to > >>> the reset_buffer_flags function to indicate if unthrottling is permitted. > >>> > >>> Alan > >>> > >> Because in my opinion, unthrottling permitted always, except release > >> last filp (tty->count == 0) > > > > Maybe so, but the patch was there in the first place to resolve an actual > observed bug, where a driver would lock up. So the behaviour needs > preserved. > > > > Andrew > > > > Maybe it was wrong driver, unfortunately, I didn't find full information > about this bug. As an example, if driver indirectly call > reset_buffer_flags() in driver's close() function it will be before > decrement last (tty->count).
Well, the driver in question was just 8250.c, so you should be able to see that the original condition can exist. Here's the commit message again: tty: fix "IRQ45: nobody cared" Unthrottling the TTY during close ends up enabling interrupts on a device not on the active list, which will never have the interrupts cleared. Doctor, it hurts when I do this. >>> On 6/2/2011 at 01:56 AM, in message >>> <20110601145608.3e586...@bob.linux.org.uk>, Alan Cox <a...@linux.intel.com> >>> wrote: > On Wed, 01 Jun 2011 10:34:07 +1200 > "andrew mcgregor" <andrew.mcgre...@alliedtelesis.co.nz> wrote: > > The LKML message > > http://kerneltrap.org/mailarchive/linux-kernel/2010/2/25/4541847from > > February doesn't seem to have been resolved since. We struck the > > issue, and the patch below (against 2.6.32) fixes it. Should I > > supply a patch against 3.0.0rc? > > I think that would be sensible. I don't actually see how you hit it as > the IRQ ought to be masked by then but it's certainly wrong for n_tty > to be calling into check_unthrottle at that point. > > So yes please send a patch with a suitable Signed-off-by: line to > linux-serial and cc GregKH <g...@kroah.com> as well. > > Alan Signed-off-by: Andrew McGregor <andrew.mcgre...@alliedtelesis.co.nz> Signed-off-by: Greg Kroah-Hartman <gre...@suse.de> What part of this no longer applies? I'm happy enough if you can prove that this can't happen any more, but otherwise the fix should remain. Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/